Gas operated rifle



July 23, 1957 J. M. MILLER GAS OPERATED RIFLE Filed June 5, 1953 L Nn n ON/ J w I INVENTOR. JOHN M. MILLER M xxx xx ATTORNEYS v. HH bull .i

United States Patent GAS OPERATED RIFLE John M. Miller, Poughkeepsie, N. Y.

Application June 5, 1953, Serial No. 359,847

3 Claims. (Cl. 89-193) This invention relates to a gas operated rifle and, more specifically, to gas operated mechanism which may be employed to operate the breach mechanism of an automatic or semiautomatic gun or rifle.

It is a known practice to employ the high pressure gases driving a bullet through a rifle barrel to actuate a piston which, in turn, serves to actuate a breech mechanism, a

cartridge case extraction mechanism and/or a cocking mechanism. Hereafter in this description the words breechmechanism will be employed as a generic term relating to any or all of these mechanisms.

In known gas operated rifles, trouble is often experienced due to the severity of the acceleration of the gas operated piston which is employed to drive an actuating rod which, in turn, serves to actuate the breech mechanismof .the rifle due to the fact that in these rifles motion of the piston cannot be delayed beyond the time at which the bullet emerges from the muzzle of the rifle because overcome the inertia and friction of the moved parts.

It is generally necessary that this acceleration be sufiiciently high to impart enough momentum to the piston and the actuating rod that they will continue their motion as the pressure within the cylinder is escaping back into the rifle barrel after the rifle barrel has become unplugged by theemergence of the bullet from the rifle muzzle.

It will be evident that in this type of mechanism the unlocking of the breech of the rifle and the extraction of the fired shell case may frequently occur before the gas pressure within the case has been entirely relieved and/ or before the walls of the case have had time to recover from the walls of the chamber thus unseizing the case from the chamber walls. During this time, if extraction of the case is attempted, the extractor may pull a piece out of the rim of the case thus failing to extract the case, the extractor or some other part of the mechanism may fracture orfail or the gun may simply stall and cease its automatic operation.

It is an object of the present invention to provide a gas operated rifle in which a gas operated actuating piston will have a rate of acceleration substantially less than that commonly encountered in this type of rifle.

It is a further object of this invention to provide a gas operated rifle in which the actuating piston will have a Ratented July 23, 1957 gas cylinder containing an actuating piston operatively associated with the rifle barrel.

Referring to the figure there is shown a rifle barrel 2 provided with a bore 4 and having at its outer end the conventional muzzle 6. The rifle barrel 2 is shown cut away at 8 in the direction extending toward the rifle breech and stock. This invention, as will become evident hereafter, may be employed with numerous types of conventional breech mechanisms and it is believed unnecessary to burden this description with details of any such mechamsm.

Positioned below the n'fle barrel 2 is a gas cylinder 10. The gas cylinder 10 is shown as positioned in axially parallel relation with the rifle barrel. While this relation will generally be maintained, it is evident that it is not necessarily retained. Slidably mounted within the gas cylinder 10 is a piston 12. The piston is machined to provide a snug sliding fit with respect to the gas cylinder and is in substantially gas sealing relation therewith. An actuating rod 14 is attached to the piston 12 and extends therefrom in the direction of the rifle breech mechanism which it may be adapted to actuate by any of numerous arrangements well known to the art.

The gas cylinder is provided with a cylinder head 16 threaded into the end thereof extending toward the muzzle of the rifle barrel and the opposite end of the gas cylinder is provided with a closure 18 through which theactuating rod 14 is adapted to pass. The actuating rod 14 is preferably in snug sliding engagement with the closure 18 so as to provide a moderately tight gas seal and to provide a guide for the actuating rod.

The piston is provided with a cavity 20 which may be in the form of a longitudinally extending bore having a suflicient volume to provide an adequate reservoir for gas to be employed as will be hereinafter described.

A member 22 is positioned between the rifle barrel 2 and the gas cylinder 10 and serves to rigidly connect these two members together. The rifle barrel is provided with a generally radially extending port 24. The member 22 is provided with a port 26 and the gas cylinder 12 is provided with a generally radially extending port 28,. The ports 24, 26 and 28 are in alignment and serve to provide a passage between the bore of the rifle andtthe inside of the gas cylinder.

A compression spring 11 is positioned between the end 18 of the gas cylinder and the piston 12 and serves to urge the piston to the right as viewed in the figure with the end rim 40 of the piston in engagement with the inwardly extending rim of the cylinder head 16. It should be noted that the spring does not necessarily have to be located inside the cylinder as described but could be behind the cylinder around the rod or could be within the breech mechanism. I v

The piston is also provided with a radially extending port 30 which is positioned to be in alignment with-the ports 24, 26 and 28 and provides communication between these ports and the cavity 20 in the piston when the piston .of the piston, as viewed in the figure, is provided with an orifice 32 having an expanding diameter portion 34 extendingto the right-hand end of the piston and providing a venturi structure as will be referred to hereafter.

To avoid an unbalanced gas pressure forcing the,pi ston against the lower wall of the cylinder as gasesenter the piston cavity, a port 31 may be provided in the piston diametrically opposite to the port 30 and/or a pressure equalizing groove 34 may be cut circumferentially 'in the outer wall of the piston connecting the ports 30 and 31 around the exterior-of the piston. It will be evident that under some conditions it may not be necessaryto sure equalizing groove 33.

'into the piston cavity 20.

When the rifle is fired and bore of a rifle passes the gas port provided by the ports 24, 26 and 28 and assumes a position in the region of the barrel between the port '24 and the muzzle 6 as indicated by the construction line bullet 36, the high pressure gas existing in the bore of-the rifle behind the bullet will pass through the'gas port and through the port 30 ports 2430 and the orifice 32 are such that the velocity of flow through the orifice 34 will reach a relatively high value only after there has been a substantial pressure build-up in the cavity 20. This high velocity flow through the orifice 34 will cause motion of the piston to the left to occur initially at a relatively low velocity. This motion will be suflicient to compress the spring to the degree 'necessary to move the piston radial port 30 out of alignment with the gas ports 24, 26 and 28 and thus the gas within the piston cavity and the gas cylinder is sealed off from the rifle barrel. By this time, however, a quantity of gas under considerable pressure will have been accumulated in the cavity 20.

The force of the spring 11, the inertia of the piston 12, the volume of the cavity 20 and the construction of the venturi 34 will be selected in conjunction with the diameter of the gas port passages 24-30 to be such that the piston cavity is sealed off from the gas port passage at the time that the bullet 36 has emerged from the muzzle of the rifle and thus, when the pressure of the gas within the bore of the rifle falls off as a result of the rifle barrel being unplugged by the bullet, the pressure existing within the piston cavity and in the gas cylinder does not drop.

As the gas under pressure contained within the piston cavity passes through the longitudinal orifice 32 and'into the cylinder, the piston is urged to the left compressing the spring 11 and simultaneously compressing air which air will serve as a cushion to reduce the impact of the "piston against the fully compressed spring 11 when the piston is at its extreme left-hand position with the gas cylinder. .Motion of the piston to the left will drive the actuating rod 14 to the left and serve to actuate the breech mechanism of the gun in a conventional manner.

A small amount of lost motion is desirably provided between the operation of the breech mechanism and the initial motion of the piston in order to permit the piston to move to the left as viewed in the figure sufiiciently far to seal off the port 30 with respect to the gas ports before operation of the breech mechanism commences thus permitting the motion of the piston for this initial degree to take place with a minimum of loading and, therefore, with a minimum of pressure required to be applied to the right-hand end of the piston. The subsequent motion of the piston compressing the spring 11 and the air contained within the chamber 38 and actuating the breech mechanism takes place after the bullet has emerged from the muzzle of the rifle. Thus the pressure is relieved from within the bore of the rifle and from within the fired cartridge case prior to operation of the breech mechanism giving the cartridge case time to contract or to unseize from the walls of the chamber before extraction thereof takes place.

As the piston is forced to the left, as viewed in the figure, the spring 11 is compressed and the air in the chamber 38 is compressed storing up energy to provide for the eventual return of the piston and actuating rod a bullet passing through the It will be evident that during an initial period of pressure build-up within the cavity 20 there will be no motion of the piston 12. After the pressure in the cavity commences to build up, a gas flow 'will occur through the longitudinal passage 32 and through the venturi orifice 34. The relative diameters of the through the ports 24--30. ,motion of the piston to its extreme right-hand or at rest to their at rest position shown in the figure and for closing or completing the operation of the breech mechanism. if desired, a port 42 maybe provided in the left-hand end of the wall of the cylinder 10 in order to provide for a partial or complete escape of the cushioning air contained within the chamber 38.

When the piston travels only a small distance to the left, as viewed in the figure, from its at rest position as shown, the port 30 will be closed off and the gas within the piston cavity and in the cylinder will be sealed off from the rifle barrel. The gas ports 24-28 and the port 34) are so positioned with respect to the end 40 of the piston that, as the piston approaches its extreme left-hand position, the end 40 of the piston moves beyond or to the left of the gas ports Z428 to a position as indicated by the construction line outline 40. The piston Will move somewhat beyond this position as a result of both its own inertia and of the pressure existing in the gas cylinder. However, when the piston reaches this position, it will be evident that the gas in the cylinder will be permitted to escape through the gas ports 2428 into the bore of the rifle which is now in open communication with the atmosphere.

A major portion of the gas pressure Within the gas cylinder is dissipated by the flow of gas from the gas cylinder back into the barrel and out of the muzzle of the rifle. The compressed spring 11 and the compressed air within the space 38 then urge the piston to the right and serve to return the piston to its at rest position at which time any remaining gas under pressure within the piston cavity will flow back into the bore of the rifle It will be evident that the position in the gas cylinder will also be cushioned by gas which is compressed ahead of the piston and which is permitted to escape into the rifle barrel only after the piston has reached substantially its extreme at rest position in the gas cylinder.

The mechanism described provides for a sufficient time delay before the actuation of the breech mechanism to permit the pressure withinthe rifle bore to be discharged and to permit the fired cartridge case to contract and becomeunseized from the chamber Walls and thus the ejector mechanism will operate freely. Furthermore, the

mechanism provides means for reducing the severity of the shock or impact of. the movable piston at either of its extreme operating positions. It will be evident that the piston motion is extremely rapid and that the impact is a substantial factor in automatic rifle operation. The hollow piston provides for the necessary time delay in the initiation of the operation of the breech mechanism and simultaneously serves to seal off the compressed gas r actuating the piston from the rifle barrel immediately after operation of the piston is commenced in order that the actuating piston may continue to operate under the effect of the compressed gas after the bullet has emerged from the bore of the rifle and the pressure within the rifle bore has fallen off.

What is claimed is:

1. In a gas operated rifle having a breech mechanism, a rifle barrel, a gas cylinder, a piston in said cylinder, actuating means operatively connected to said piston for actuating the rifle breech mechanism, means yieldingly urging said piston toward one end of said gas cylinder, a cavity in said piston, an orifice in said piston having a cross-sectional area substantially less than that of said cavity and providing restricted communication between said piston cavity and the end of the cylinder toward which said piston is urged by said urging means, and means providing for the passage of gas. under pressure from said rifle barrel behind a bullet passing therethrough to said piston cavity, gas from said cavity passing through said orifice, displacing said piston against said urging means and driving said actuating means.

2. In a gas operated rifle having a breech mechanism, a rifle barrel, a gas cylinder, a piston in said cylinder, actuating means operatively connected to said piston for actuating the rifle breech mechanism, means yieldingly urging said piston toward one end of said gas cylinder, a cavity in said piston, an orifice in said piston pro viding communication between said piston cavity and to end of the cylinder toward which said piston is urged by said urging means, and means providing for the passage of gas under pressure from said rifle barrel behind a bullet passing therethough to said piston cavity, gas from said cavity passing through said orifice, displacing said piston against said urging means and driving said actuating means, said piston orifice being in the form of the a jet orifice to provide jet reaction against the piston upon the passage of gas therethroughto move the piston and close off said passage means before the pressure of the gas in said gas cylinder becomes equal to the pressure of the gas in said cavity.

3. In a gas operated rifle having a breech mechanism, a rifle barrel containing a bore for the passage of a bullet, a gas cylinder positioned adjacent to said barrel, a movable piston in said gas cylinder, actuating means operatively connecting said piston with the rifle breech mechanism, means yieldingly urging said piston toward one end of said gas cylinder, a cavity in said piston, a generally longitudinally extending orifice in said piston of smaller diameter than said cavity extending between said cavity and the end of the piston adjacent to the end of the gas cylinder toward which said piston is urged by said urging means, a generally radial port in said piston extending between said cavity and the side Wall of said piston,

means providing a gas port extending between the bore of said barrel and the interior of said gas cylinder, said gas port and said radial piston port being in substantial alignment when said piston is at rest providing for the admission of gas under pressure from the bore in the rifle barrel into the cavity in said piston upon the passage of a bullet through said barrel past said gas port, said piston being movable against the urging of said urging means by the gas under pressure passing from said piston cavity through said piston longitudtinal orifice into the gas cylinder to first close ofi the passage formed by said gas port and said piston radial port before the pressure of the gas in the rifle barrel falls off as a result of the bullet emerging from the muzzle thereof and thereafter to open said gas port to the gas cylinder beyond the orifice end of said piston when said piston has moved to substantially its extreme displaced position in said gas cylinder to permit the escape of the gas under pressure in said cylinder into said rifle barrel after the pressure of the gas within the barrel has fallen off as a result of the emergence of the bullet therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,401,667v Brown Dec. 27, 1921 2,382,411 Green Aug. 14, 1945 2,409,225 Schaich Oct. 15, 1945 2,482,880 Sefried Sept. 27, 1949 2,714,334 Harvey Aug. 2, 1955 FOREIGN PATENTS 48,141 Austria May 26, 1911 547,851 Great Britain Sept. 15, 1942 

